This invention relates generally to terminal block assemblies for electrical power distribution, and, more particularly, to filtered terminal block assemblies for removing undesirable frequencies from electronic signals.
A growing proliferation of electronic devices in modern products and systems can produce unintended and undesirable signal distortion between electrical components, systems and subsystems. While some signal distortion is tolerable in many instances, in certain applications signal distortion is a significant issue that must be controlled, if not overcome. Such applications wherein reduction and/or elimination of signal distortion is desirable include, for example, power supply systems for telecommunication systems, telecommunication switching applications, cellular base stations, radar transmission systems, industrial control systems, and instrumentation systems.
Consequently, a variety of terminal block assemblies have been introduced that include one or more filter elements coupled to electrical terminal elements for removing undesirable frequency transmission through the terminal block. One type of filtered terminal block assembly includes a tubular capacitor element mounted to a terminal stud for filtering a signal through the stud. When electrical connections are made to the terminal stud in the field, however, the tubular capacitor element may be placed under a structural load. Connections to threaded studs render this type of terminal block assembly particularly vulnerable to placing the capacitor element under stress when a wire is fastened to the stud. The resultant stress may damage the capacitor element and adversely affect filtering performance of the terminal block assembly.
U.S. Pat. No. 6,371,791 discloses a terminal block assembly having a filter assembly with a tubular capacitor filtering element for filtering a signal through the stud. The filter assembly is mechanically isolated from a base assembly with a resilient contact element extending longitudinally between the terminal stud and the filter assembly. Structural loading of the filter assembly when electrical connections are made to the terminal stud is therefore avoided and reliable filtering of signals is ensured in a cost effective manner. Such terminal blocks, however, are presently limited to approximately 10,000 pF (picofarads) of capacitance. Higher capacitance levels are desired for certain applications to improve attenuation characteristics of the terminal blocks.
At least one type of terminal block exists which is capable of providing capacitance levels of about 2 μF (microfarads) using laminated foil materials to fabricate capacitive elements for filtering of signals passing through the terminal block. The manufacture of such terminal blocks, however, is difficult and equipment intensive. It would be desirable to provide a lower cost alternative terminal block which is capable of providing capacitance levels in the range of about 2 μF.